My 01 does the same thing but only when a lot of current is drawn from the battery(in cold weather) to start the engine or if it sits in my garage for more than 4 0r 5 days without running, because of battery getting trickle discharged from my alarm.
Sometimes is pretty bad that it also beeps. But its only the battery so I don't worry about it.
Check for anything that may be discharging your battery.

 

That would explain why I only notice it when it's colder out and not in the summer.

 

Mine does it at idle only. It does it after the engine reaches operating temps. As soon as I touch the throttle it goes away.

 

If I've only noticed mine on startup, I'm assuming it's a weak battery.

 

replaced diode pack on my alternator to fix this on mine.
The original battery had gone bad causing the diode pack in my alternator to go bad, hence the pulsating dash. New battery did not fix it, had to replace the diode pack.

 

if it flickers with your idle, it's your alternator diode pack (rectifier) like ronnuke said. mine did the same flickering thing and i replaced it with a used alternator, which fixed the problem.

mine only flickered once warmed up and idling at 1000 rpm or less. cold starts and any rpm higher than 1000 stopped the flickering.

 

same thing happend to my 07....but i didnt replace the alternator. i bought a new rectifier assembly and replaced it. flickering went away.

 

yea i was thinking about doing that too, but getting my hands on a used alternator was much cheaper than getting the rectifier thing from honda for me.

 

I posted a video

start up video

 

Mine is JUST like that.